Abstract of Research Supplement For an intervention to be effective, patients must adhere to its prescribed behavioral or cognitive changes. One factor that may impact such adherence is memory for treatment. Unfortunately, memory for treatment is often poor, particularly for health behavior change advice. We cannot act on advice we cannot remember, and so the proposed research supplement seeks to investigate the impact of The Memory Support Intervention, designed by the parent R01, on behavioral and cognitive change. By designing a mixed-methods interview, called The Cognitive Behavior Change Interview, and administering it to participants of the parent R01, the proposed research supplement examines the relationship between memory support and targets of behavior change outlined in the Theoretical Domains Framework. These targets, referred to as domains, are taken from 33 theories of behavior and are the building blocks of behavior change. Over a 2-year period, 60 adults with Major Depressive Disorder who successfully completed Cognitive Behavioral Therapy (CBT) in the parent R01 will be interviewed. We will compare the effects of CBT-as-usual to CBT+Memory Support to determine if The Memory Support Intervention better engages behavior change domains compared to CBT-as-usual. This research will contribute to the science of behavior change by identifying how we might better facilitate change in mental health interventions, and by bringing a stronger focus to the interplay between behavior and memory. !